The present invention relates to a coupling for transmitting torque between a driving part and a driven part. The coupling has a hydraulic displacement system which is arranged between the two parts. The displacement system acts against relative rotational movements of the two torque loaded parts relative to one another. The displacement system includes a housing with an internally trochoidal housing casing and two housing covers. Also, an externally trochoidal rotor rotatably held in the housing. The housing and rotor each are connected to one of the torque loaded parts and form a sealed inner chamber which is at least partially filled with a fluid. A displacer, in the shape of a trochoid casing, is arranged between the housing casing and the rotor is guided between the trochoidal face of the housing casing and the trochoidal face of the rotor. The displacer divides the inner chamber relative to the housing casing and relative to the rotor into inner and outer chamber regions. One extra trochoidal tooth is provided on the trochoidal face of the housing casing relative to the displacer and on the displacer relative to the trochoidal face of the rotor.
Coupling assemblies are used in drivelines of motor vehicles and land machinery to generate a locking torque between two rotating parts as a function of a speed differential.
A first application refers to differential drives where the coupling is arranged between two parts which rotate relative to one another in the case of differential movements. As a result of the coupling, the differential drives have a partial locking effect.
A second application refers to the driveline of a motor vehicle with a plurality of driven axles, with the coupling fitted directly in the driveline. As a result, the respective driveline is torque-loaded only if a speed differential occurs between its driven axle and a rigidly driven further axle, whereas otherwise, its axle is driven dragged along by the vehicle.
A coupling is known from U.S. Pat. No. 4,658,583 in which the two inner and outer chamber regions each form a displacer pump. The two pumps are connected with a consumer by means of a regulating and control system. In a known way, the device constitutes two trochoid pumps which are used for the power-assisted steering system of a motor vehicle.
A coupling of a similar type is shown in JP 4-27269. The coupling is connected to a differential drive in such a way that the housing is integral with the differential carrier, whereas the rotor is non-rotatably positioned on one of the axle shafts. Every differential movement between the axle shafts of the differential drive results in a relative movement between the housing and rotor of the coupling. By displacing the enclosed viscous fluid and as a result of its return flow through the sealing gap between the rotor and housing, it is possible to generate a partial locking effect of the differential. The locking effect of the coupling can only he adjusted by means of the tolerances between the housing and rotor, which, in view of the standard production accuracy, is an inaccurate method of adjustment.